As a method useful for producing particles of an acrylic polymer, a suspension polymerization method is known. According to the suspension polymerization method, slurry of an acrylic polymer after polymerization is appropriately dehydrated and washed, and after subjecting it to a step like drying, particles of an acrylic polymer are produced. The particles of an acrylic polymer are used as a raw material of a coating composition, a raw material of an ink composition, a binder for a copy machine toner, a binder for ceramic calcination, an intermediate raw material of a thermoplastic resin, or the like.
With tendency of having low electric conductivity and large specific surface area, the particles of an acrylic polymer have a property of easy electrostatic buildup. Because it is easy for the particles of an acrylic polymer with electrostatic buildup to have low fluidity, there are cases in which blocking inside a pipe of a manufacturing plant or poor sieve device passability is caused by them. Furthermore, there are also cases of having a problem in handlability when the particles of an acrylic polymer are in a state of electrostatic buildup. Electrostatic buildup may easily occur after a drying step of the particles of an acrylic polymer. Due to those reasons, a method for suppressing electrostatic buildup during a step after the suspension polymerization is suggested.
For example, a method of providing conductivity according to a chemical treatment of a surface of particles of an acrylic polymer, a method of reducing friction among acrylic polymers by carrying out drying using a vacuum dryer or the like so that the electrostatic buildup may hardly occur, a method of drying the particles of an acrylic polymer with humidified air, a method of removing electrostatic buildup by carrying out an electric treatment of the particles of an acrylic polymer with electrostatic buildup, or the like are suggested.
However, those methods are problematic in that large amounts of money are required for facility investment or operation, process management is cumbersome, production rate is slow, or the like.
Accordingly, as a method for convenient and low-cost production of the particles of an acrylic polymer with excellent fluidity due to suppressed electrostatic buildup, in Patent Literature 1, for example, a method of washing the particles of an acrylic polymer after suspension polymerization with water in which electrolytes are dissolved at 1 to 1000 ppm is described.